October 14, 2013

Global Warming And The Future Of El Nino

A new study published in the journal Nature says that climate change could have a negative impact on the El Niño-Southern Oscillation (ENSO) weather pattern. El Niño occurs in the Pacific Ocean and is an important part of the world's climate system, and new research shows how rising temperatures could affect the weather pattern in the future.

During El Niño, the eastern and tropical Pacific regions of the planet warm up, while during La Niña these areas get a little chillier. These weather patterns are responsible for rainfall patterns across Australia and the equatorial region as well as during the Northern Hemisphere's winter.

Scientists have been concerned about how this weather pattern could be affected by rising temperatures as a result of climate change, and the latest study shows the outcome may not be good.

"The El Niño–Southern Oscillation (ENSO) drives substantial variability in rainfall, severe weather, agricultural production, ecosystems and disease in many parts of the world," the authors wrote in the study. "Given that further human-forced changes in the Earth’s climate system seem inevitable, the possibility exists that the character of ENSO and its impacts might change over the coming century."

Although scientists have been looking into this issue for the past two decades, there has been very little consensus on future changes in El Niño, apart from an expectation that the weather pattern will continue to be a dominant source of year-to-year variability.

"Here we show that there are in fact robust projected changes in the spatial patterns of year-to-year ENSO-driven variability in both surface temperature and precipitation," the researchers wrote. "These changes are evident in the two most recent generations of climate models, using four different scenarios for CO2 and other radiatively active gases."

The team predicted that by the mid-to-late twenty-first century, the western Pacific Ocean will experience intense El-Niño-driven drying, while the central and eastern equatorial Pacific will see rainfall increases.

"Experiments with an Atmospheric General Circulation Model reveal that robust projected changes in precipitation anomalies during El Niño years are primarily determined by a nonlinear response to surface global warming," the team wrote. "Uncertain projected changes in the amplitude of ENSO-driven surface temperature variability have only a secondary role. Projected changes in key characteristics of ENSO are consequently much clearer than previously realized."

Dr Wenju Cai, a scientist at the Commonwealth Scientific and Industrial Research Organization (CSIRO), told BBC that this research is significant because there is stronger agreement among different climate models in predicting the future impact.

"This study finds that both wet and dry anomalies will be greater in future El Nino years. This means that ENSO-induced droughts and floods will be more intense in the future," Cai said.